Aluminum-titanium dioxide filled thermoplastic resin compositions



United States Patent M 3,224,997 ALUMENUM-TETANTUM DTOXHDE FILLEDTHERMGPLASTHC RESHN CUMPGSHTTQNS Paul H. Hunter, Highland Park, NJ,assignor to Union Carbide Corporation, a corporation of New York NoBrawing. Continuation of appiication Ser. No. 587,210, May 25, 1956.This appiication Mar. 23, 1062, er. No. 182,112

Claims. (Ci. 26041) This application is a continuation of my earlierapplication entitled Thermoplastic Resin Compositions, Serial No.587,210, filed May 25, 1956, which is now abandoned.

This invention relates to thermoplastic resin compositions, and has forits principal object novel compositions having improved (higher)opacity, good characteristics of color and good physical properties.

Opaque thermoplastic resin compositions are used to prepare film, sheet,coatings, molded and extruded sections of all sorts; laminar structuresand the like which go into a large number of divers applications suchas: shower curtains; draperies; upholstery sheeting; Wall tile; floortile; venetian blind slats; tapes; plastic playing cards; constructionpanels; containers; instrument housing; kick plates; coatings on paper,cardboard, metal foil and other substrates; instrument scales; dialfaces; and many others. The numerous applications in which opaquethermoplastic resin compositions are employed present a variety ofproblems which may be generally summarized as follows:

(1) To provide light colored, particularly white, thermoplastic resincompositions having greater opacity;

(2) To provide thermoplastic resin compositions having greater opacityand adequate degrees of such physical properties as impact strengthfiexural fatigue resistance, and printability;

(3) To provide a light colored, particularly white thermoplastic resincompositions having a higher degree of opacity and adequate degrees ofsuch physical prop-. erties as impact strength and flexural fatigueresistance.

Heretofore, opacity has been achieved by loading pigments into the resincomposition, with titanium dioxide, the preferred pigment and opacifierfor white compositions. This method and the resultant compositions areinadequate in several respects.

Many resin compositions, including those containing mixtures of apolyvinyl chloride or vinyl chloride-vinyl acetate copolymer, and thevinyl chloride-octyl acrylate copolymer resins, cannot be madesufliciently opaque for exacting applications with any reasonable amountof titanium dioxide. In all cases, the degree of opacity which can beachieved with titanium dioxide is limited. Opacity increasesprogressively with increasing titanium dioxide concentration up to aboutto 20%; but higher concentrations of titanium dioxide provide relativelylittie additional opacity. Moreover, concentrations of titanium dioxideover about 18 to 20%, have an adverse effect on several importantproperties.

Compounds containing up to about -18% Ti0 have better calenderingcharacteristics than the corresponding unpigmented compositions; buthigher concentration, i.e., more than about 18 to 20%, degradecalendering behaviors. For instance, at about Ti0 content, the calenderroll banks become so rough and finger so badly (e.g., becomediscontinuous with part of the bank sep arating away from the main bank)as to make the opera- 3,224,997 Patented Dec. 21, 1965 tion difficult atbest, and in the case of rigid compositions, impractical.

Any amount of TiO (and other such fillers) tends to degrade flexuralfatigue life; but the fiexural fatigue life of compositions containingas much as about 18% TiO is still generally acceptable for mostapplications, but compositions containing more than about 18% to 20% TiOare not generally acceptable for those numerous applications in whichthe film or sheet must have a flexural fatigue life equivalent to theability to sustain about 50,000 flexural cycles when tested by themethod hereinafter described in Example 1.

Titanium dioxide imparts a yellowish tone which is often undesirable andmust be masked with color toners, and which increases with increasingTiO concentration. This yellow tone is especially objectionable in whitecompositions at about 20% or more TiO content.

High TiO concentrations are expensive, because of the cost of thepigment itself and because it increases product density appreciably andthereby increases the weight of material required to cover a unit area.

The opacity provided by titanium dioxide cannot be increased to anysignificant extent either by using more rigorous compounding proceduresdesigned to provide superior pigment dispersion, nor by using auxiliarypigments and fillers such as antimony oxide, .zinc oxide, calciumcarbonate and the like in combination. with the titanium dioxide.

On the other hand TiO addition improves impact strength, with themajority of the improvement realized by the time the TiO content is upto about 20% to 25%. Still higher concentrations, up to about 36%provide substantially no further improvement; and at still higherconcentrations, impart drops off rapidly. Because of this favorablecontribution to impact strength, the presence of up to about 18% to 20%,and in some special cases even up to about 25% TiO is desirable.

This invention is based on the discovery that a relatively smallproportion of aluminum pigment in combination with concentrations oftitanium dioxide pigment (or substantially equivalent other whitepigment such as zinc oxide) within the general range customarily used,imports greatly increased opacity to thermoplastic resin compositionswithout imparting physical properties or color.

All thermoplastic resins and mixtures are usable in this invention.Typical of the resins and resin mixtures which have given particularlygood results are the following: (1) 3:1 mixture of vinyl chloride-vinylacetate copolymer with vinyl chloride-octyl acrylate copolymer; (2)vinyl chloride (90%)vinyl acetate (10%) copolymer with vinyl chloride(85 %)vinyl acetate (15%) copolymer; (3) a polyvinyl chloride resin; (4)a polyethylenc resin, (5) a :30 polystyrenezrubber mixture, and (6) aplasticizecl polyvinyl chloride resin composition.

Commercial aluminum powders and pastes of both the leafing andnonleafing variety are useful. Commercial grades of aluminum powderfrequently contain up to about 5% aluminum oxide or up to about 3% of alubricant such as stearic acid or both. Such grades are also suitable.Best results are generally obtained with those powders and pastes inwhich the aluminum particle size is such that the covering area on waterof the metal content is from about 7,000 to about 25,000 squarecentimeters per gram, as determined by the method of Edwards and Mason(Ind. Eng. Chem, Anal. Ed, vol. 6, p. 159, May 1934). Smaller particlesizes, such as are used in extra fine lining pastes and the like, i.e.,water covering value about 30,000 sq. cm./ gm. and above, cause anunfavorably greater degree of greying. With larger particle size gradessuch as are referred to as flitters and the like, i.e., water coveringvalue less than about 3,000 to perhaps 6,000 sq. cm./gm. individualparticles are discretely visible and impart a speckled appearance to theproduct.

The preferred concentration of aluminum as a percentage of the entirecomposition, is as follows:

(a) About 0.01% to 0.1%, usually not over 0.05%, for light and pastelcolored, including white, compositions;

(b) About 0.01% to 0.3% for dark colored compositions and forapplications in which color and impact requirements are not stringent.

Range (a) provides combinations of opacity, color (e.g., whiteness),impact strength, fiexural fatigue resistance, printability and printretention, hitherto unattainable. Range (b) provides opacity and thepreviously cited fiexural fatigue and cost advantages attendant on usinglower Tl02 concentrations.

The broadest useful range of concentration of titanium dioxide is about2.5% to 25%. About 6% to 20% provides a good balance of opacity, color,strength, etc.; and the optimum balance of said properties is generallyobtained with about 12% to 18%, all on the basis of the entirecomposition as 100%.

When present in concentrations up to about 0.1% aluminum imparts a bluecast which is preferable, particularly in white compositions, to theyellow cast imposed by high concentrations of titanium dioxide. Whenpresent in concentrations of about 0.1% and above, Al imparts a greycast which intensifies with increasing Al content. Impact strength dropswith increasing Al concentration up to about 0.1%. Additional aluminum,i.e., over about 0.1%, has substantially no additional effect on impact.

The opacifiers can be incorporated into the thermoplastic resincomposition by any of the methods generally used to mix and compoundsuch thermoplastic resin compositions such as by mixing in paddle type,ribbon or-conical blenders, on two roll mills, in Banbury and otherscrew type mixers, in extruders, and by other known methods. In largerscale operations, it is advisable to prewet the aluminum powder toprevent its dusting and forming explosive aluminum-in-air suspensions.The aluminum can be prewetted with one of the liquid components of thecomposition such as the stabilizers, lubricants or plasticizers. In theabsence of liquid components, it may be wetted with a small amount,about its own volume, of an inert liquid such as mineral oil or waterwhich may be allowed to remain in the composition or removed during thesubsequent mixing and compounding operations. Alternatively, it can bewetted, mixed into a small amount of resin and the wetting agentremoved; and this aluminum-resin concentrate or masterbatch can then beincorporated into the thermoplastic resin composition in any of theusual manners.

EXAMPLE 1 Seven 4- lb. mixtures (samples A to G) each consisting of 56.6parts by weight of a vinyl chloride-vinyl acetate copolymer containing90% vinyl chloride, 18.9 parts of a vinyl chloride-octyl acrylatecopolymer containing 80% vinyl chloride, 18 parts titanium dioxide, 0.5part trioctyl phosphite, 3.0 parts of the diglycidyl ether of2,2-bis-(p-hydroxyphenyl)-propane, 2.0 parts basic carbonate of whitelead, 1.0 part of 60:40 barium-cadmium 'laurate, and the number of partsshown in Table I of aluminum powder having an average covering capacity(on water) of 17,000 sq. cm./gm. as determined by the method of Edwardsand Mason, Ing. Eng. Chem, Anal. Ed, 6, 159 (May 1934), were processedand tested in the following manner.

The entire mixture was blended in a paddle mixer or ribbon blender forabout 10 minutes at room temperature, mixed and fluxed in a Banburymixer for about 5 minutes under 10 to 20 p.s.i. ram pressure and withcooling Water circulating through the Banbury rotor and jack et at sucha rate that the mass temperature rose gradually to about C. during thisinterval; fiuxed and sheeted on a C. two-roll mill and end-passed fivetimes thorugh the bight of said mill; then calendered into 4.5, 8 and 10mil sheet on a 4-roll, inverted L type calender. Calender speed wasvaried from about 20 to 40 ft./min. depending on film thickness desired.All of the compositions calendered satisfactorily at all sheetthicknesses and calendering speeds.

Sections of the 4.5 mil calendered stocks were press polished down to4.0 mils; and the light transmittance of these smooth-surfaced, 4.4 milspecimen was measured with a Gardner haze meter according to the methodof ASTM D-1003-52, Procedure A. The results are shown in Table I.

Sections of the 8 and 10 mil calender stocks were compression moldedtogether into an homogeneous 8 inch X 8 inch x 0.125 inch sheet and Izodimpact strength test pieces were then cut from said sheet, notched andtested according to ASTM D25643T.

Card specimens, 2 /4 inch x 3 /2 inch, cut from the 10 mil stocks, weretested for flexural fatigue life in the following manner. A deckconsisting of 25 cards was placed in a De Mattia flex tester with the 2%inch ends clamped in the rubber covered tester jaws and flexed at therate of 120 cycles per minute. After 10,000 cycles, a few cards wereremoved, each was folded in half; the fold was creased sharply betweenthumb and forefinger; and the crease, which was parallel to the 2% inchedges and mid way between them, was examined for cracks, breaks andother defects indicative of failure. The original population of the deckwas restored by adding the requisite number of fresh cards thereto; thereplenished deck subjected to an additional 10,000 cycles; and a fewcards which had endured the full 20,000 cycles, i.e., not replacementcards, were removed, folded, creased and examined as before. Theoriginal population of the deck was again restored with fresh cards, anadditional 10,000 cycles were imposed, and the above-describedobservation and flexing sequence was repeated until fatigue was manifestby the presence of a significant number of failing cards. Flexuralfatigue lifes determined in this manner are shown in Table I.

Sections of the 10 mil sheet stocks prepared from compositions ofsamples A and B were provided with a uniform matte finish by pressplanishing them at C., then cut to size, printed and spray lacquered bythe standard technique used to make playing cards. The two sets ofspecimens were substantially equivalent to each other and at least asgood as commercial thermoplastic playing card stocks with respect toprintability, resistance of the print to removal by stripping withpressure sensitive tape, and ink retention under abrasion such as occurswhen the cards are slipped over each other in play.

For comparison, eight mixtures, samples H through 0, were processed andtested in substantially the same manner as samples A to G. With respectto compositions H to 0, each contained the same vinyl chloride-vinylacetate copolymer resin and vinyl chloride-octyl acrylate copoly- Table11 Sample II I I K L M N O T102 (percent) 6 12 18 24 30 36 42 LightTrausmittance (per- Compositions H, I, I and K calenderedsatisfactorily. In the case of L, however, the calender banks weresomewhat rough and some fingering took place. These deficiencies wereprogressively more severe with M, N and O, in that order. Fingering isthe term given to the formation of a fingerlike roll of material whichseparates from the main bank. This behavior requires considerableattention by the operator to maintain continuous operation and causesthickness irrregularities and other quality deficiencies in the product.Also, compositions M, N and 0 did not feed evenly into the calender, alimitation which would generally make them unacceptable for continuousprocessing; and continuous attenion was necessary to maintain theuniform feed needed to provide the representative homogeneous samplesrequired for test purposes.

From the foregoing observations and the results shown in Tables I andII, it can be seen that the use of appropriate combinations of aluminumand titanium dioxide provides numerous advantages which cannot beachieved with TiO alone.

The new TiO Al combinations of this invention can be used advantageouslyto opacify thermoplastic compositions containing virtually anythermoplastic resin and virtually any of the plasticizers, stabilizers,antioxidants, lubricants, processing aids, colorants and other modifiersvariously used in such compositions. This is illustrated by thefollowing example.

EXAMPLE 2 The compositions were processed and 4.0 mil press polishedtest specimens were prepared in substantially the same manner describedin Example 1. The light transmittance of said specimens was measuredwith an Integrating Sphere Photometer per ASTM D-1003-52,

Procedure A.

I II

Composition (percent by weight):

Polystyrene, percent 20. 0 20. 0 60% Polystyrene40% GRS- 60. 1 60.0 Zincstearate 0. 55 0. 55 2,G-di-tert-butyl-p-cresol 0. 35 0. 35Tris-nonylphenyl phosphite. 1. 00 1. ()0 Titanium dioxide 18. 0 1S. 0Aluminum powder 0 0. Light Transmittauce (percent) 8 4 III IV Comosition ercent by weight):

P hlyethyle ie 8]. 7 81. 6 Zine stearate 0. 2 0. 2 p-Tertiaryamylphenol/form aldeliyde 0. l O. 1 Titanium dioxide 18. 0 18. 0Aluminum powder 0 0. 1 Light 'lransmittance (percent) 9 4 Composition(percent by Weight):

90%viuyl chloride-l0% vinyl acetate copolymen. vinyl chloride-15% vinylacetate copolymer. Dibutyl tin laurate maleat Dibutyl tin dilaurateSalol was Stearic acid. Titanium dioxi Aluminum powder LightTransmittance (percent) The optimum proportions of T102 and aluminumdepend on the particular resinous composition and end-use for which saidcomposition is intended. By way of illustration, relatively thicksections, about 40 to mils thick, of thermoplastic resin compositionsare used for wall tile. Consequently, materials employed in this andsimilar applications need not ordinarily be as opaque as those employedin thinner sections such as are used for playing cards, instrument facesand the like; and a light transmittance (measured on a 4.0 mil sheet asdescribed in Example 1) of the order of 10% is generally acceptable.This degree of opacity can usually be attained with about 03-01%aluminum is combined with about 4 to 10% TiO By way of furtherillustration, opaque polyethylene compositions are frequently extrusioncoated onto paper, cardboard and other substrates to hide the flaws andimperfections of said substrated. For such purposes, compositions havinga light transmittance (measured on a 4.0 mil film as described inExample 1) of about 6% are generally acceptable. Used in this manner,i.e., as an extrusion coating onto paper, a composition consistsing of94 parts polyethylene resin, 0.1 part ditert-butyl-p-cresol (DBPC), 6parts TiO and 0.05 part aluminum was substantially equivalent to acomposition consisting of 85 parts of the same polyethylene resin, 0.1part DBPC and 15 parts Ti0 with respect to masking effectiveness.Moreover, the former composition was superior to the latter with respectto covering powder per unit weight, economy and fiexural propertiesbecause of its lower titanium dioxide content.

Metallic aluminum, in the form of powder, flakes, or paste has been usedin thermoplastic resin compositions for metalizing, as a colorant(grey), as an opacifier, in combination with p-tert-butylphenol as astabilizer and for other reasons. However, all such prior uses differfrom the present invention with respect to at least one of the hereindescribed simultaneous requirements of aluminum concentration, aluminumparticle size, and corn joint use of the aluminum with TiO (or otherwhite pigment).

Unless otherwise specified, all parts and percentages mentioned hereinare by weight.

What is claimed is:

1. An opaque pigmented calenderable normally solid thermoplastic resincomposition consisting essentially of a thermoplastic resin, and inintimate admixture therein titanium dioxide pigment and a particulatemetallic aluminum pigment, said titanium dioxide pigment being presentin an amount of from about 2.5 to about 25 percent by weight based onthe total weight of the pigmented resin composition, and said metallicaluminum being present in an amount of from about 0.01 to about 0.10percent by Weight based on the total Weight of the pigmented resincomposition and being of a particle size such that the covering area onwater is from about 7000 to 25,000 square centimeters per gram.

2. The composition of claim 1 wherein the thermoplastic resin is apolyethylene resin.

3. The composition of claim 1 wherein the titanium dioxide is present inan amount of from about 6.0 to about 20 percent by weight based on thetotal weight of the pigment resin composition.

4. The composition according to claim 11 wherein the titanium dioxide ispresent in an amount of from about 12 percent to about 20 percent byweight based on the weight of the pigmented resin composition and themetalg; lic aluminum pigmented is present in an amount of from about0.01 to about 0.05 percent based on the total Weight of the pigmentedresin composition.

5. The composition according to claim 4 wherein the thermoplastic resinis a polyethylene resin.

References Cited by the Examiner UNITED STATES PATENTS 2,850,490 9/1958Canterino et al. 260-41 2,878,145 3/1959 Aid et al 26041 3,041,3036/1962 Nelson 260-4l MORRIS LIEBMAN, Primary Examiner.

ALEXANDER H. BRODMERKEL, Examiner.

1. AN OPAQUE PIGMENTED CALENDERABLE NORMALLY SOLID THERMOPLASTIC RESINCOMPOSITION CONSISTING ESSENTIALLY OF A THERMOPLASTIC RESIN, AND ININTIMATE ADMIXTURE THEREIN TITANIUM DIOXIDE PIGMENT AND A PARTICULATEMETALLIC ALUMINUM PIGMENT, SAID TITANIUM DIOXIDE PIGMENT BEING PRESENTIN AN AMOUNT OF FROM ABOUT 2.5 TO ABOUT 25 PERCENT BY WEIGHT BASED ONTHE TOTAL WEIGHT OF THE PIGMENTED RESIN COMPOSITION, AND SAID METALLICALUMINUM BEING PRESENT IN AN AMOUNT OF FROM ABOUT 0.01 TO ABOUT 0.10PERCENT BY WEIGHT BASED ON THE TOTAL WEIGHT OF THE PIGMENTED RESINCOMPOSITON AND BEING A PARTICLE SIZE SUCH THAT THE COVERING AREA ONWATER IS FROM ABOUT 7000 TO 25,000 SQUARE CENTIMETERS PER GRAM.